Discontinuous ply for runflat tire construction

Abstract

The innermost carcass ply of a runflat tire ( 50 ) having a radial carcass ply is a discontinuous ply ( 52 ) that includes two portions ( 52 a , 52 b ) each disposed within one of the sidewalls ( 43, 45 ). In one embodiment, each of the two discontinuous ply portions is composed of two layers ( 64, 66 ) of cross-biased cords ( 65, 67 ) which are disposed be-tween the two wedge inserts ( 58 b , 59 b ) in each side-wall. In another embodiment, the two portions ( 72 a , 72 b ) of the discontinuous ply ( 72 ) are composed of wavy metal cords. In athird embodiment, a runflat tire incorporating either embodiment of the discontinuous ply ( 92 a , 92 b ) is built using the locked, tie-in construction for the carcass ply.

What is claimed:  
     
       1. A pneumatic radial ply runflat tire having a tread; two sidewalls; a carcass comprising an outer radial carcass ply, two bead regions each containing an inextensible annular bead, at least two plies contained in each sidewall and two distinct wedge inserts in each sidewall; and one or more belts located between the tread and the outer radial carcass ply, the tire being characterized In that: 
       one of said at least two plies being a two-part discontinuous ply comprised of two portions, wherein one portion is in one sidewall between the two distinct wedge inserts and the other portion is in the other sidewall between the other two distinct wedge inserts, each of the two portions of the two-part discontinuous ply is made from two layers of cross-biased fabric;  
       each of the two cross-biased fabric layers is made of parallel-aligned cords;  
       the parallel-aligned cords of a first fabric layer are oriented at an angle with respect to the radial direction that is approximately equal in magnitude but opposite in direction to the parallel-aligned cords of a second fabric layer of the two layers of cross-biased fabric; and  
       the parallel-aligned cords of the respective fabric layers are oriented at angles of between 40 degrees and 65 degrees with respect to the radial direction.  
     
     
       2. The tire or  claim 1  characterized in that: 
       the parallel-aligned cords of the respective fabric layers are preferably oriented at angles of between about 45 and 55 degrees with respect to the radial direction.  
     
     
       3. The tire of  claim 1  characterized in that: 
       the parallel-aligned cords of the respective fabric layers are made of materials from the class of materials that includes nylon and rayon.  
     
     
       4. The tire of  claim 1  characterized in that: 
       turn-up ends of the outer radial carcass ply are substantially contiguous with the main structural portion of the outer radial carcass ply.  
     
     
       5. The tire of  claim 4  characterized in that: 
       the free ends of the ply turn up ends extend from above the corresponding bead upward to the mid-height of the sidewall.